Two-way vibratory conveyors or feeders have substantial applications in a variety of fields. One typical application is in foundry operations. For example, castings may be delivered to the conveyor at a location intermediate its ends and then the conveyor energized to feed the castings to one end or the other depending upon where it is desired to locate the casting.
A typical two-way conveyor made according to the prior art by the assignee of this application will typically include an elongated bed with an upwardly facing, generally horizontal conveying or feeding surface terminating at opposite ends. The bed is supported on isolation springs adjacent the ends which in turn serve to elevate and mount the bed above the underlying terrain, such as the floor in a factory building or the like.
Two motor and weight assemblies are secured to the bed generally centrally thereof. Each will usually include a squirrel cage motor having a rotary output shaft to which is secured an eccentrically mounted weight. Springs in the form of plastic or fiberglass slats connect each of the motors to the bed. The motor and weight systems are typically canted at approximately 45 degrees to the bed with one being canted in one direction and the other being canted in the opposite direction. In operation, to convey in one direction, one of the systems is energized and vibration resulting from eccentric revolution of the weight associated therewith will cause flow along the bed in one direction. When it is desired to convey or feed in the opposite direction, that system is de-energized and the other motor and weight system is energized.
In many applications, it is not unusual that there is a considerable disparity between the amount of use of the two motor and weight systems. When that occurs, so called "false brinnelling" of the motor bearings in the motor associated with the least used motor and weight system will occur as a result of the vibration imparted to the bed. Lubricant may be squeezed out of the bearings as a result. As a consequence, when that system is finally energized, it may fail relatively quickly as a result of bearing failure caused by the false brinnelling and the resulting insufficient lubrication of the bearings.
Moreover, in foundry applications, it will be necessary that the bed be formed of metal to stand up to continued pounding of castings. In a prior art system such as described, vertical acceleration of the conveying or feeding surface during operation will typically exceed that of gravity. As a result, after the conveying surface has reached its highest point of movement in a cycle, it will be accelerated downwardly more rapidly than a casting or the like on the surface. The casting will be temporarily suspended above the surface but will eventually collide with the same as movement of the surface begins to reverse while the casting is being moved downwardly under the influence of gravity. The result is a noise producing impact of the casting upon the metal of which the bed is formed, the level of which will typically be undesirably high.
It will also be appreciated that the provision of two motor and weight systems when only one is used at any given time adds considerably to the cost of the apparatus.
In U.S. Pat. No. 3,746,149, there is proposed a reversible vibratory feeder that utilizes but a single motor and weight system. Feed direction is changed by tuning dynamic vibration absorbers in the form of air springs. This system eliminates some of the difficulties associated with the system previously described but is unduly complex in that at least eight air springs and considerable associated piping along with control valves is required. Consequently, it, too, is costly and difficult to use.
The present invention is directed to overcoming one or more of the above problems.